Pathogenesis of "senile" nodular sclerosis of atrio-ventricular valves.

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Abstract
The pathology and pathogenesis of nodular senile sclerosis of the atrio-ventricular valves was studied. At least a slight nodularity was found at the line of closure of all adult mitral valves. The degree of thickening increased throughout middle age in both atrioventricular valves, but showed little further progression in the elderly. It differed widely between people of the same age-group, and the normal appearances, even over 85 yr., consisted of slight nodular thickening of the mitral valve only. The location and histology of the thickened foci indicated that they were a response to repeated impact, analogous to cutaneous callus formation. There was no associated endocarditis or atherosclerosis. Excessive nodular thickening was not related to senility, systemic hypertension, cardiac hypertrophy, or multiparity, but chronic pulmonary disease was associated with a significantly increased degree of thickening in both atrio-ventricular valves. Abnormal degrees of nodular thickening appear to result from an abnormal response of valvular endothelium. Although genetic factors cannot be excluded, it is suggested that in man, as in rats, hypoxia is important in the pathogenesis of nodular sclerosis of the atrio-ventrieular valves.